Certain number of persons are sitting in a linear row from west to east and facing in the north direction.
Two persons sit between H and M.
D sits third to the left of M.
Three persons sit between H and K.

R sits immediate right of K.
R sits at one of the ends of the row.
Thus, Case 2 gets cancelled.

Four persons sit between M and A.
The number of persons sitting to the left of F is equal to the number of persons sitting to the right of R.
This is the final arrangement.
Four persons are sitting between M and F.
In the same way, four persons are sitting between H and R.